It is well-known that media data is, to different degrees, vulnerable to channel errors when transmitted through an imperfect communication channel. For example, chunks of data may be lost due to transmission errors. One known method used to conceal the effects of data blocks transmission errors relies upon estimating or interpolating contents of lost blocks utilizing relationships between this content and the content of neighboring blocks. However, estimation and interpolation methods do not comprehend the actual content of lost data blocks, and the effectiveness of these methods decreases as the distance between a lost block and the available neighboring blocks increases. Thus, audible artifacts can often be detected after recovery.
Reliable transmission of digital audio over packet-switched networks such as the Internet that offer no quality of service (QoS) guarantee is a challenging task. Although channel coding can be used to protect the audio from packet loss, this type of protection increases the payload and thus requires extra bandwidth to transmit the audio stream. On the other hand, known methods of error concealment extract features from the received audio for use in the recovery of lost data. Error concealment methods are attractive because perceptual audio quality is improved without the need for additional payload.
By extracting audio features from an audio stream at an encoder and transmitting these features to a decoder along with the audio stream, both the computational complexity of receivers for error concealment and inaccuracies in the extraction of enhancement features by decoders can be reduced. Such transmission methods, however, suffer from many of the same disadvantages of channel coding and may not be useful at all because the feature transmission stream similarly increases the payload. Not only does the extra payload require increased bandwidth, but the extra payload also necessarily modifies the audio format if neither a common area nor a user data area is available. Because of the required format change, ordinary decoders can no longer decode the audio stream.